Method of producing white oils



Patented Sept. 18, 1945 METHOD OF PRODUCING WHITE OILS Clyde M. Floyd, Baytown, and Julius Fram, Goose Creek, Tex., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application February 14, 1944, Serial No. 522,394

7 Claims.

The present invention is directed to a method for treating petroleum stocks to produce White oils.

VVhit-e oils obtained from petroleum are commonly used for medicinal purposes and for the lubrication of food-handling machinery. It is desirable that white oils be entirely stable and water-white in color. It is also desirable that the oil retain its stability so that it will not carbonize when subjected to elevated temperatures when used in lubricating food-handling machinery.

In the manufacture of white oils by the methods of the prior art, it is usual to subject an essentially parafifinic fraction, such as a middle distillate having a viscosity in the range of 75 second t 300 seconds at 100 F., or a raffinate obtained from such middle distillates by solvent extraction, to treatment with a plurality of dumps of fuming sulfuric acid. The acid sludge resulting from each dump or increment of the acid is removed before the oil is contacted with the next dump of acid and after the treatment with the last dump of acid the sulfonic acids present in the oil are removed by washing with water or with aqueous alcohol. After the washing step or steps the oil is neutralized by means of caustic soda and then finished by contacting it with clay. The. acid-contacting steps are usually carried out at temperatures no greater than slightly above atmospheric. This conventional method of treating petroleum stocks for producing white oils requires an excessive amount of fuming sulfuric acid, and many times fails to produce a satisfactorily stable white oil.

It is an object of the present invention to re-v fine predominantly paraflinic petroleum stocks to obtain a stable white oil. More specifically, it'is an object of the present invention to treat predominantly paraffinic petroleum stocks with sulfuric acid of less concentration than fuming acid,

and to obtain by this treatment white oils of improved stability.

parafiinic fraction is refined to produce a white oil by treating it with successive increments of sulfuric acid having a concentration less than fuming. After each increment of acid is added to the oil and agitated therewith, the mixture is allowed to settle to separate an oil fraction and an acid sludge fraction, and the acid sludge fraction is drained off and the oil fraction then washed with a small amount of water. This washing step removes sulfonic acids from the oil fraction and, upon settling, the aqueous solution of sulfonic acids is withdrawn from the oil. The oil is then dried by means of a small amount of acid, known as the acid-cutter dump, and this acid is also removed from the oil by settling. The step of adding a portion of the acid-settling and removing the acid sludge and washing is then repeated until the total acid to be used has been applied to the oil. After the last increment of acid is added to the oil and the acid sludge separated, the oil is washed several times with water. The oil is then dried by blowing with a hot gas at a temperature between about 25 and 300 F. and contacted with clay at asuperatmospheric temperature. The oil withdrawn from the cla is a stable white oil, ready for marketing.

The procedure described in the preceding paragraph may optionally be modified (by omitting the step of drying the oil after the washing steps with the exception of the washing after the final acid dump, and to this end the useof the acidcutter dump after these washing steps may be omitted. When the procedure is modified in this manner, a good quality white oil is obtained. In most instances, however, more effective use of the sulfuric acid is obtained by following each washing step with a drying step.

The sulfuric acid employed for treating the oil may have a concentration ranging from to 98% H2804. This acid may be commercial sulfuric acid, or, if desired, may be obtained as spent acid withdrawn from an alkylation or similar process. The temperature of treatment may be in the range between atmospheric temperatures and 200 F. The amount of acid used per unit of volume of oil treated, the temperature of treatment and the number of increments of acid employed may be varied over a considerable range. It has been found satisfactory, when treating a raflinate obtained from the extraction with phenol of a middle distillate having a viscosity of 100 seconds at 100 F., to employ three successive clumps of 100 pounds each of spent alkylation acid at a temperature of F. per barrel of oil. After each acid dump the acid sludge was drained off and the sulfonic acids precipitated from the oil fraction by washing it with 5% by volume of water. The oil was then dried by contacting it with a (i-pound per barrel acid-cutter dump and the cutter acid withdrawn. After the last acid dump and removal of the acid sludge, the sulfonic acids were removed and the oil purified b washing it several times with 5% by volume of water. The oil was dried by blowing it with hot natural gas at a temperature of 275 F. and then contacted with clay for a period of 30 minutes at a contact temperature of 300 F.

The white oil obtained by the example above described was superior in quality to white oils obtained from the same rafiinate by the use of cone ventional acid treating methods. The superiority of the white oil produced in accordance with the present invention is shown by the data in the following talble. Column I shows the characteris: tics of the henol rafiinate used as a charging stock. Column II shows the treatment of the phenol rafiinate with three dumps of spent alkylation acid, as above described, and gives the characteristics of the white oil obtained from this method of treatment. Column III also shows the treatment of the phenol raffinate in accordance with the present invention, in which only 200 pounds of spent alkylation acid was employed in three dumps for treating the oil.

Column IV shows the treatment of the phenol rafiinate in accordance with previously known acid treating methods, 300 pounds of acid in three dumps being used, but the steps of washing the oil after each acid dump being omitted. This run is directly comparable with that of column II inthat equal amounts of acid were used in an equal number of dumps. It will be seen, however, that the omission of the washing steps after each acid dump results in a white oil in run IV which does not satisfy the requirements set out in the specification in column A. The treatment shown in column V omitted the Washing steps after each dump, but involved a substantially heavier acid treatment than in the preceding runs, but this additional acid failed to pro runs, but that this additional contact time failed 7 to produce a satisfactory white oil.

furic acid too weak to employ in the conventional methods for obtaining white oils; in fact, the acid used in the present treatment may be that discarded as spent acid from other chemical processes, such as alkylation.

It may be pointed out that particularly good results are obtained when treating paraffinic oils of the character of oils obtained as raflinates in solvent extraction processes. However, other predominantly parafiinic fractions may be treated in accordance with the present invention, but such fractions will usually require more acid than the raifinates produced by solvent extraction. In

. general, oils having viscosities ranging from 75 seconds to 350 seconds at F. may be treated in accordance with the resent invention for the production of stable White oils. The treating reagent may be either commercial sulfuric acid ranging from 85% to 98% H2804 or spent acid of approximately the same strength, or a mixture of these acids. The amount of acid required may vary with the charging stock, but in general it is in the range of 200 to 300 pounds of acid per barrel of oil.

The temperature of the treatment may range from atmospheric to 200 F. and the pressure may be atmospheric or, if desired, may be less or greater than atmospheric. It will be understood that the amount of acid employed, the concentration of the acid and the pressure and temperature of the treatment may be varied over a substantial range and satisfactory results will be obtained throughout the range.

Having fully described and illustrated the practice of the present invention, what we desire to claim is:

1. A method for producing white oils comprising the steps of subjecting a predominantly paraffinic petroleum stock to successive treatments with sulfuric acid, separating acid sludge from the oil and washing the oil with water after each acid treatment, and finishing the acid treated oil by drying and contacting with clay at temperatures substantially above atmospheric.

2. The method of obtaining white oils comprising the step of treating a predominantly paraffinic petroleum fraction with a plurality of acid dumps, separating acid sludge from the oil arfter each acid dump and washing the oil with water after the separationof the acid sludge and before the addition of the succeeding acid dumps, and

Treatment III IV V Spent g lky. acid (88% H 80 lbs. H2SO4/bb]. of oil at 98% black acid, lbs. H SO /bbl. of-oil Acid dumps Soaps ppt. between dumps.

Clay, lbs/gallon lay used Contact time, min Contact temp, F

Gravity, API Specific gravity.

7 USP acidity USP sulfur USP carbonizable 1 Does not pass.

These data indicate that the treatment of the present invention produces a white oil superior to that obtained by conventional methods. This superior product may be obtained when using sulfinishing the acid treated oil by drying and contacting with clay at temperatures substantially above atmospheric to obtain a stable white oil.

3. A method for obtaining a white oil comprising the steps of treating a rafiinate fraction with sulfuric acid having a concentration ranging from 85% to 98% H2804 in a plurality of stages, removing acid sludge in each stage, washing the oil with water after each acid treating step, finishing the acid treated oil by drying and then contacting with clay at superatmospheric temperatures.

4. A method for preparing a white oil comprising the steps of treating a predominantly paraffinic rafiinate with sulfuric acid having a strength ranging from 85% to 98% H2804, removing the acid sludge from the oil, then washing the oil with water, contacting the oil a second time with sulfuric acid in approximately the same amount and same strength as in the first treatment, re moving acid sludge from the oil and washing the oil with water, treating the oil a third time with sulfuric acid in approximately the same amount and same strength as in the first two treatments, the total amount of sulfuric acid used in the three treatments ranging from 200 to 300 pounds of acid in a barrel of oil, removing the acid sludge from the oil after the third treatment, washing the .oil with water, drying it and contacting the dried oil with clay at super-atmospheric temperatures to produce a stable white oil.

5. A method for refining a petroleum fraction comprising the steps of treating a predominantly paraflinic rarfinate having a viscosity ranging from '75 seconds to 300 seconds at 100 F. with 100 pounds of sulfuric acid at 160 F., separating acid sludge from the acid treated oil, washing the acid treated oil with water, contacting the acid treated oil with sulfuric acid in a second step using the amount and concentration of acid and temperature of treatment used in the first step, separating acidsludge from the acid treated oil and washing the acid treated oil with water, contacting the acid treated oil with sulfuric acid in a third acid treating step using the same amount and concentration of acid and temperature of treatment used in the preceding step, separating acid sludge from acid treated oil and washing the oil with water, drying the acid treated oil (by contacting it with gas at a temperature in the range of 250 to 300 F., then contacting the oil with clay for not less than 30 minutes at a contact temperature of about 300 F. and separating the oil from the clay to obtain a finished white oil.

6. A method in accordance with claim 5 in which the acid treated oil is washed with 5% by volume of water after each acid treating step.

7. A method for producing a white oil comprising the steps of admixing a predominantly paraflinic fraction obtained as a rafiinate by solvent extraction and having a viscosity of 105 seconds at 100 F. with 100 pounds of sulfuric acid, settling to obtain an oil fraction and an acid sludge fraction, withdrawing the acid sludge fraction, washing the oil fraction with 5% by volume of water, drying the oil fraction, contacting the dried oil fraction in a second acid treating step with pounds of sulfuric acid, settling to obtain an oil layer and an acid sludge layer, withdrawing the acid sludge layer, washing the oil layer with 5% by volume of wa er, drying the washed oil layer, contacting the dried oil layer with an additional 100 pounds of sulfuric acid in a third acid treating step, settling to obtain an oil layer and an acid sludge layer, withdrawing the acid sludge layer, washing the oil layer a plurality of times with water, subsequently blow-, ing the washed oil with gas having a temperature in the range of 250 to 300 F. to dry the oil, and contacting the dried oil with clay for at least 30 minutes at a temperature of approximately 300 F. and separating the oil from the clay.

CLYDE M. FLOYD. JULIUS FRAM. 

